“Much of their breeding and wintering habitat is gone,” says Scott C. Yaich of the conservation group Ducks Unlimited, and the animal’s primary breeding-season food — beech mast, the nuts of a beech tree — is limited.
The birds “simply couldn’t be restored to a landscape that is so radically altered from the one to which they were uniquely adapted,” says Yaich, director of conservation for Ducks Unlimited.
But Mark Twery, a research forester at the U.S. Forest Service, says that though beech bark disease has reduced beechnut production, “the overall quantity of forested habitat is likely to be ample to support a large enough number of pigeons for a viable population, even should people be able to restore the species.”
Other experts say that given the nesting behavior of the passenger pigeon, releasing a handful of birds into the wild would be a losing proposition.
The mainstream view of passenger pigeon ecology is that they used a reproductive strategy called predator satiation. The recent cicada invasion is one example of this strategy. Each cicada is individually easy to catch in its slow, bumbling flight. But there are so many millions of cicadas in a spot at one time that they are able to finish mating and laying eggs before predators have had time to eat all of them. If only a few thousand cicadas emerged at once, then most of them would probably be eaten before they were able to reproduce. In this way, the cicada’s survival depends on showing up in hordes.
Passenger pigeons succeeded through a similar sort of mob rule. Individually, their behavior was borderline reckless. They built flimsy nests, often dangerously low to the ground. The nests were built so hastily that when bad weather would slow down construction, a female would sometimes be forced to lay her eggs on the ground. When the young were ready to leave the nest — after only 14 days of development — they would spend their first few days on the ground, vulnerable to any hungry predator.
Passenger pigeons could get away with such behavior because of their incredible numbers. When a flock arrived at a nesting area, predators could gorge themselves for weeks. Each pair of nesting pigeons would produce two eggs, at least one of which usually ended up on the ground. But even with the constant work of foxes, bears, possums, raccoons, hawks, eagles, snakes and other meat-eaters, enough of the young pigeons survived to fly away.
This system works great with a flock of 5 million birds. But according to Kirk Mantay, a biologist specializing in habitat restoration, if only a few thousand pigeons show up, the whole system falls apart.
“If you put 5,000 out there, even with good habitat, they could all still be gone in a few decades unless you could exclude the predators somehow and make sure that they nested right where you wanted them to go. You just couldn’t make enough birds for it to work.”
A handful of nests and fledglings might escape the notice of predators, but as soon as the colony grew to a few dozen nests, the noise and scent would bring those predators in to feast on easy meals. You would need to skip ahead to millions of birds for the predator satiation strategy to properly work.
Still, “I believe the passenger pigeon will survive because we have people committed to its survival,” Novak says, citing the reintroducton of the condor into the wild in California. In that case, the birds, on the verge of extinction, were bred in captivity, then gradually released beginning in the 1990s; there are now about 200 living in the wild.
Would a commitment to its survival be enough to sustain the passenger pigeon? A few specimens living in an aviary would be a historic accomplishment. But an effort to put the passenger pigeon back into the wild would be challenging at best.
“Habitat restoration is hard to get right for species like turkey and quail that we know about,” says Mantay. “How long is that going to take with something we can’t study in the wild first?”
There may be other species that could be resurrected, animals that can survive in smaller numbers with less habitat. The Carolina parakeet might have a chance, with federal protection. The woolly mammoth could do very well in a herd of a few dozen within a large park, living at least as wild as bison in Yellowstone. As for the passenger pigeon, science may permit us to mourn it all over again.
Landers is the author of “The Beginner’s Guide to Hunting Deer for Food” and “Eating Aliens.”